Electrical coil



June 21, 1932.

n l. N. WHITESMITH ELECTRICAL COIL Filed Nov. 13. 1930 F'i g. 5.

lnvetor: 'ISOLQC N..\^/hibesmth, bg MM His ther-neg.

Patented June 2l, 1932 .UNITED STATES PATENT OFFICE y ISAAC NEWTONWHITESMITH, 0F URMSTON, ENGLAND, ASSIGNOR TO GENERAL ELEC- TRIO COMPANY,A CORPORATION 0F NEW YORK ELECTRICAL COIL Application. led November 13,1930, Serial No. 495,465, and in Great Britain November 30, 1929.

My invention relates to electrical coils, more particularly toelectrical coils such as are used in electrical instruments, voltage orcurrent transformers, radio applications and the like, and has for itsobject the provision of an improved coil of this character and method ofmaking it.

Electrical coils are commonly wound on a former consisting of a tube ofpaper or other insulating material provided with flanged ends so as toform a bobbin, and when the coil is provided with paper or other sheetinsulation between the layers it is usually necessary to leave a spaceof at least of an inch between the wire and the ilanges inl order thatthe wire forming one of the end turns of any particular layer may notbecome displaced and make contact with a wire in another layer of thewinding and thereby incur the risk of a breakdown of insulation owing toan unduly high potential difference existing between the two wires; theactual length of the coil is therefore increased beyond that which isactually necessary to contain the desired number of turns of wire.

In making a coil in accordance with the present invention, the wire iswound upon a tube without end flanges and the several layers in the coilare separated by paper or other suitable sheet insulating material whichserves to hold the wire in place and extends to a distance beyond eachend of the layers.

At the ends of the coil thus formed in the interstices between the endsot the sheets of the paper an insulating material in powdered form,which is capable of being moulded by heat under pressure such, forinstance, as a powdered resin of the phenol-formaldehyde type, issprinkled and then the ends of the paper are compressed being folded upand crinkled with the powder filling the crevices.

The coil thus prepared is inserted in a mould which is closed and heatapplied to consolidate the powder. The mould which is used inconsolidating the powder may be employed for compressing the ends of thepaper. The leads from the coil can be led out through slots provided inthe mould for that purpose. By this means the coil is formed with solidends or cheeks which, by regulating the qualitity of mouldable powderemployed, vmay be as thick as desired.

In the improved coil manufactured as above described space is economizedasl a. clearance between the end turns of eachy layer and the end iangesis not required, the layers of in'- sulation are held securely by theirends and the turns of the winding are held firmly in position.

The sheet insulation employed in winding the coil must be such as willstand the temperature required for moulding the material forming theends. Conveniently, paper either untreated or varnished with a solutionof a resin of the phenol-formaldehyde type may be employed or clothuntreated or treated with this solution for heavier wires.

In order that the nature of my invention may be clearly understood anexample of how the same may be carried into practical effect will now bedescribed in some detail with reference to the accompanying drawing inwhich: Fig. 1 is a diagrammatic sectional view showing a. portion of theendturns of a coil with the associated sheet insulating material afterit is wound; Fig. 2 is a similar view, but illustrates the same at alater stage in the manufacture; Fig. 3 is a section of a mould in whichthe powdered insulating material can be consolidated by heat underpressure` the coil being illust-rated in position in the mould; and Fig.4 is a diagrammatic elevation of a completed coil, parts being brokenaway to illustrate certain details of the construction of the coil.

In making the coil in accordance with my invention the wire is woundwith insulating sheet material, paper or insulating cloth for example,between the layers, but the layers of wire do not extend to the edges ofthe paper. This is clearly indicated in Fig. 1 wherein the end turns 10of three layers of a conductor are shown in section, togetherv withsheets vof paper insulation 11 interposed between adj acent layers, theedges of these sheets projecting beyond the end turns, as is clearlyshown on the left-hand side of the drawing. It will be understood thatthe coil may be thus wound by hand, or may be wound in any suitablewinding machine (not shown) After the required number of turns have beenwound, powdered insulating material, which is capable of beingconsolidated by heat under pressure, such as that having as a base aphenolic condensation product, is sprinkled in the interst-ices of thepaper at the two ends of the coil.

The coil is then put in an annular mould indicated at 12 in Fig. 3 inwhich the edges of the paper at each end of the coil are shown at 13,the wire wound portion being indicated at 14; and an annular plunger 15is forced down by a press so as to compress the ed es of the paper withthe insulating pow er therebetween somewhat as indicated 1n Fig. 2, inwhich 16 indicates the powdered insulatin material.

he mould is then closed and heated to the proper temperature toconsolidate the insulating material after which the coil is removed andappears somewhat as shown in Fig. 4. The ends of the winding are led outat 17 and the coil may be covered with paper or cloth or other materialon the outside as indicated at 18.

If desired the coil may be covered with moulded insulated material onthe outside as well as at the ends by providing space in the mould atthe outside and inside of the coil for holding the insulating powder.

It will be observed that in the completed coil the moulded insulatingmaterial forms the flanges which are close to the end turns of the wire,all of which are held firmly in position.

While I have shown a particular embodiment of my invention, it will beunderstood, of course, that I do not wish to be limited thereto sincemany modifications may be made, and I, therefore, contemplate by theappended claims to cover any such modifications as fall within the truespirit and scope of m invention.

at I claim as new and desire to secure by Letters Patent of the UnitedStates is 1. The method of making an electrical coil which compriseswinding the turns of said coil on sheet insulating material so that theend portions of said sheet insulating material project beyond the endturns of said coil and then compressing the projecting portions of saidsheet insulating material inwardly toyward said turns and compactingsaid compressed portions with an insulating material so as to formflanges for said winding.

2. The method of making an electrical coil which comprises winding theturns of said coil on sheet insulating material so that the end portionsof said sheet insulating material project beyond the end turns of saidcoil, applying to the end portions of said coil a mouldable insulatingmaterial, and then compressing said projecting end portions inwardlytoward said layers of turns and moulding said insulating material aboutsaid compressed end portions so as to form end llanges for said coil.

3. The method of making an electrical coil which comprises winding eachlayer of turns of said coil on a sheet of insulating material so thatthe end portions of said sheet project i beyond the layer of turns woundthereon, ap-

plying to the end portions of said coil thus formed an insulatingmaterial having the characteristic of assumin a moulded form upon theapplication of heat and pressure, subjecting said winding to pressure sothat said projecting end portions and sai d insulating material arecompressed inwardly toward sa1d layers of turns and then applying heatto said winding so as to mould said insulating material whereb saidcompressed end portions are secured7 and said end ortions together withsaid moulded insulating material orm end flanges for lsaid coil.

4. The method of making an electrical coil which comprises winding eachlayer of turns of said coil on a sheet of insulating material so thatthe end ortions of said sheet project beyond the end) turns of the layerwound thereon, a plying to the end portions of said coil thus ormedpowdered insulating material which is capable ofbeing consolidated bythe application of heat and pressure, ap,- p ying pressure so as tocompress said projecting end portions and to compact said powderedinsulating material about said compressed portions and then applyingheat while the pressure is maintained so as to mould said insulatingmaterial whereby said compressed end portions are secured and said endportions together with said moulded insuliting material form end flangesfor said co1 5. The method of making an electrical coil which compriseswinding each layer of turns of said coil on a sheet of insulatingmaterial so that the end portions of each sheet project beyond the endturns of the layer wound thereon, filling the interstices between saidprojecting end portions with a regulated quantit of powdered insulatingmaterial which as the characteristic of assuming a moulded form whensubjected to pressure and heat, subjecting said winding to pressure soas to press said projecting end portions inwardly toward the said endturns of said layers and to compact said powdered insulating materialwithin the crevices of and about said compressed end portions, and then'applying sucient pressure, and heat at a suiciently high temperature tocause said powdered insulating materialto assume a moulded form.

6. The method of making an electrical coil which com rises winding eachlayer of turns of said coi upon a sheet of insulating material so thatthe end portions of each sheet project beyond the end turns of the layerwound thereon, applying to the projectm end portions and to the surfacesofthe co5 thus formed an insulating material ping the characteristics ofassuming a moulded form u on being subjected to heat and pressure, thensubjectin said coil to pres- 5 sure so that the projecting end portionsof said sheet insulating n material are pressed inwardly toward thewound layers of said coil and then subjecting the coil tokheat andpressure so as to mould said insulating material about said coil.

7. The method of making an electrical coil which comprises winding eachlayer of turns of said coil on a sheet of insulating material so thatthe end portions of said sheet pro- 16 ject beyond the layer of turnswound thereon, applying to the end portions of said coil thus formed aninsulating material havin the characteristics of assuming a moulde formupon the application of heat and pres' 20 sure, subjecting said coil topressure so that said projecting end portions and said insulatinmaterial are compressed, then a plying eat to said coil so as to mouldsaid insulating material, and then covering said coil with a protectivecover.

8. An electrical coil comprising a conductor wound into a plurality oflayers each layer being wound on a sheet of insulating material, the endportions of which are compressed and compacted in an insulating compoundso as to form end flanges for said coil.

9. An electrical coil comprising a conductor wound into apluralityoflayers, sheets of insulating material interposed between as saidlayers, said sheets being longer than said layers and having their endportions com-A ressed inwardly toward said layers and an,

insulting material moulded about said compressed end portions so thatsaid insulatin o materialtogether with said comp en portions formflanges for the-end turns of said layers. L C Y 10. An electrical coilcomprising an electrical, conductor wound into a plurality of 5 layers,sheet insulating material interposed between said layers, each sheetbeing longer than its associated layer and having its end portionscompressed inwardly toward the endturns ofvsaid la er, and anelectricall o insulating compoun compacted about saicompressedend-portions so that said insulatin compound together withsaid com ressed- -v engl portions' form ianges for the en turnsA v ofsaid layers and an electrically insulating compound compacted about theremaining surfaces of said coil.v In witness whereof, I have hereuntoset my hand this 27th day of October, 1930. f ISAAC NEWTON WHITESMITH.

